Heating device



" 22,1967 w. w; BUECHNER I 3,337,714

HEATING DEVICE Fil ed Feb. 5-, 1964 N82 ans United States Patent3,337,714 HEATING DEVICE Werner W. Buechner, 4407 Cladding Court,Midland, Mich. 48640 Filed Feb. 3, 1964, Ser. No. 342,197 9 Claims. (Cl.219331) This application is a continuation-in-part of my copendingapplications Ser. No. 23,313, filed Apr. 19, 1960, now Patent No.3,124,051, and Ser. No. 52,524, filed Aug. 29, 1960, now Patent No.3,236,649.

This invention relates to a method and apparatus for producing a streamof temperature conditioned water, and more particularly, to a processand apparatus for the provision of a flowing temperature conditionedmedium, to be used in photographic treating processes and inphotographic treating apparatus.

Most photographic treating processes, and particularly the photographicdeveloping methods used in the production of actual images from latentimages, contained on photographic materials, require some kind oftemperature control of the treating media, if it is desired to obtainpredictable or reproducible results. Temperature control is of paramountimportance in the development and other treatment of the multilayerphotographic color materials. Most of the complex multistep colorprocesses, such as those used for the development of color negativefilms, color reversal films, and the processes used for the productionof color positive paper prints or positive transparencies from negativeor positive originals require extremely close temperature control,particularly in the first developing step. Usually, absolute temperatureconstancy within /2" F. is desirable for best results. Depending on thenature and origin of the material, temperature control within 1 to 2 F.is desirable in most of the succeeding steps. Various methods anddevices are commercially available which permit the control of thetemperature in the said photographic treating process within the statedlimits.

However, most of the available apparatus and devices are, because oftheir high price or because of the nonavailability of suitable watersupplies and other reasons not accessible to the amateur who intends toproduce occasionally a few color prints or who intends to developoccasionally one or a few color films. The relatively high initial costof the commercially available automatic mixing devices, their dependencyon a source of running cold and hot water and the time consuming initialadjustment of the desired temperature by trial and error show theexistence of a need for a method and apparatus which provides a streamof running water of a predetermined, essentially constant temperaturewhich method is simple to practice also by the inexperiencedphotographic amateur with apparatus and devices which are inexpensiveand readily available.

It is therefore the primary object of the present invention to provide aprocess which produces a stream of water of a predetermined constanttemperature, requiring merely a source of running cold water and asource of electricity.

Another object of the invention is the provision of inexpensiveapparatus and device capable of providing a stream of water having apredetermined constant temperature.

Additional objects of the invention will become apparent from theaccompanying drawings and from the following description of theinvention. The objects of the invention are accomplished by a methodwhich comprises the steps of contacting a stream of essentially constantflow rate of a liquid medium, having an essentially constant temperaturelower than said desired constant temperature with at least one heatingmeans and controlling the heat output of said heating means such thatthe heat supplied to said stream of liquid medium essentially equals theheat energy required for continuously heating said streaming liquidmedium to the said desired higher temperature.

The liquid medium preferred in the process of the invention is waterfrom a supply which delivers a stream of Water of an essentiallyconstant temperature which temperature is lower than the desiredtemperature. The heating means employed in the process of the inventionare preferably electric heaters and most advantageously electric iInmersion heaters which are completely or at least with their heatedparts immersed in the flowing stream of heating medium. Though theprocess may be practiced with a single heater having the requiredheating capacity, it was found to be of great advantage if amultiplicity of heaters is employed, which may be individually energizedor deenergized as is needed. For more accurate control, at least one ofthe heaters should be provided with means which permit the variation ofthe power input in a wide range and preferably in a range from zeroinput to the full rated input. If desired, a thermostatic control meansmay be used as the means for the variation of the power input or morethan one heater may be provided with means permitting control of thepower input and/or with thermostatic control means.

A stream of liquid medium of essentially constant flow rate may beconveniently produced in accordance with the present invention byflowing the liquid medium through an orifice at an essentially constanthydrostatic pressure. The preferred process of providing a stream ofliquid medium of an essentially constant flow rate comprises the stepsof maintaining a column of liquid medium of a predetermined, essentiallyconstant height over an orifice through which the metered liquid mediumflows. Conveniently, the column of essentially constant height isprovided by flowing liquid medium to said column at a rate which exceedsthe rate at which the liquid medium emanates from said orifice anddisregarding the excess of liquid medium overflowing at the top of thecolumn. If desired, other means may be used for the maintenance of anessentially constant hydrostatic pressure at said orifice.

The invention comprises also a device which comprises essentially aheating chamber, means for the provision of a stream of a liquid medium,means adapted to pass said stream of liquid medium through said heatingchamber and heating means provided in said heating chamber and adaptedto supply the heat energy required for heating said stream of liquidmedium to a predetermined higher, essentially constant temperature. Theheating chamber is preferably a receptacle, having an inlet and outlet,located such that the liquid medium passes preferably in a vertical orin an essentially vertical direction through said receptacle. Ifdesired, the heating chamber may be comprised of a multiplicity of cellsfor the containment of the multiplicity of heating elements. Additionalmeans for mixing the heated liquid medium or for equalizing the flow ofthe heated liquid medium are with advantage provided in the heatingchamber or in the conduit for the heated liquid medium.

The present invention concerns also a device adapted to supply acontinuously flowing stream of liquid medium of essentially constantflow rate which device comprises a receptacle or conduit having aninlet, an outlet comprised of an orifice of predetermined aperture sizein a low position in said receptacle and overflow means at a positionessentially higher than said outlet. The said receptacle is preferablyoblong and advantageously vertically oriented and the said inlet isdesirably located at a position away from said outlet, so thatturbulence or eddying motion of the streaming liquid medium above thesaid outlet is re- C9 duced to a minimum. If desired, bafiles or othermeans capable of reducing turbulence or eddying motion in the liquidmedium flowing in said receptacle are provided in said receptacle.

The process and the apparatus and device of the invention areparticularly useful for the maintenance of an essentially constanttemperature in photographic treating apparatus and particularly in aphotographic bath containing at least one treating and/ or wash vessel,in which the temperature conditioned liquid medium may advantageouslyserve also as the washing medium. Any part of the apparatus and devicemay be integrated with such photographic treating apparatus. For mosteffective operation of the process, the streaming temperatureconditioned liquid medium is flown in the said photographic treatingapparatus in an essentially vertical flow pattern and preferably in suchmanner that it flows by the walls of said treating vessels and, ifapplicable, through said wash vessel in an essentially verticaldirection.

Further embodiments and modifications of the process, device andapparatus of the present invention are described in my Patent No.3,124,051 and in the following detailed description and in theaccompanying drawings, wherein:

FIG. 1 is an isometric water metering device.

FIG. 2 is a vertical section of an embodiment of a heating chamber takenalong line 1212 of FIG. 3,

FIG. 3 is a horizontal section of the heating chamber taken along line13-13 of FIG. 2, and

FIG. 4 is a schematic representation of a variable transformer modifiedin accordance with the present invention.

The novel process and apparatus of the present invention may be widelyused in combination with photographic liquid treatments, and especiallywith the development of photographic positive and negative film andsheet materials such as films, reversal films and paper base materials.The process and apparatus of the present invention are especially usefuland beneficial if they are used in combination with the more recentlyintroduced multistep photographic developing and treating processesavailable for the processing of color positive and negative multilayercolor film and sheet material. My invention includes many modes ofoperation and many modifications of the process and apparatus which makeit particularly suited for application in combination with the saidmultistep color developing processes.

Prefatory to a detailed description of the process and apparatus of theinvention some of the more important terms used herein will be explainedin order to provide a better understanding of the nature of theinvention and of its scope.

The term essentially constant temperature as used herein is meant todesignate a narrow temperature range falling around a desired orpredetermined constant temperature. Depending on the particular use towhich the temperature conditioned liquid medium provided by the processand apparatus of the invention is put, the permitted deviation from thedesired temperature may vary to a difi'ferent degree. For some usesvariations of F. are acceptable. For other uses the variation should notexceed :2 F. For most exacting uses, such as in color developingprocesses, the variation of the temperature should not exceed :1 F. andpreferably be not more than /2 F. Variations of the temperature from thedesired or predetermined value by the just described values fall underthe term essentially constant temperature.

Temporary variations, exceeding these limits are not critical and arepermissible, provided they are for short periods of time only inrelation to the total time of operation, because a streaming medium isused a the temperature conditioning medium in accordance with theinvention. The medium travels rapidly through the receptacle view of anembodiment of the or other containers where it is used as thetemperature conditioning medium so that constantly new portions ofmedium contact the photographic vessel or other containers in which thetemperature is to be kept essentially constant.

The phrase essentially constant flow rate refers to a flow rate whichdoes beneficially not vary more than :10 percent from a predeterminedvalue over longer periods of time. Preferably, the flow rate does notvary by more than :5 percent and for most exacting uses, it should notvary by more than :3 percent from a predetermined value.

The novel water and temperature control device of the invention operatesubstantially on the following principles. Water taken from the groundor from the faucet of the conventional water supply lines generallyhasafter it has run for a certain length of time and after the waterlines and other parts of the supply system, through which the runningwater passes have taken on the temperature of the running water--asubstantially constant temperature, which is usually lower than theprocessing temperature required for most photographic processes. Manycolor developing processes are adjusted to be carried out mostaccurately at a standard 75 F. temperature. Only in extreme cases suchas in heat waves in summer will the tap water in some localities have atemperature, which exceeds the recommended processing temperature justmentioned. Thus, generally the addition of heat energy will be necessaryto raise the temperature of the water supply to the level of the desiredprocessing temperature. Equal amounts of water of constant temperaturerequire identical amounts of heat energy in order to raise thetemperature of the running stream of water to a constant highertemperature. In the practical operation, it is only necessary to measurethe temperature of the water supply and determine, by simplecalculation, the heat energy required for the desired increase of thetemperature of the water passing at a'constant, predetermined rate overthe source of heat energy. As long as the three factors, namelytemperature of the water supply, amount of water supplied to the heatingmeans per time unit and amount of electrical energy supplied andconverted into heat energy are kept constant, the temperature of thewater emerging from the heating device will be constant and exactly atthe predetermined and desired level.

The principles of this novel process of the invention can be put intopractice by help of simple steps and apparatus. The first step in theprocess comprises opening the water supply line and taking a fewreadings of the temperature from time to time. As soon as thetemperature of the emerging water has reached a constant level, whichwill normally be the case after about 5 to 15 minutes running time,depending on the local circumstances and on the time of the year, afinal reading of the temperature is taken and recorded as Temperature A.Conveniently, the thermometer indicating the temperature of the tapwater, is built into the water supply line. By well-known physicalprinciples, the amount of Water flowing by gravity through an orifice ofgiven size is dependent on the hydrostatic pressure of the water at thelocation or level of the orifice. Conversely, at constant hydrostaticpressure, constant amounts of water per time unit flow out of an orificeof controlled size thus providing a flow of water at constant rate. Bythe application of this principle, viz. keeping the hydrostatic pressureof a free flowing water supply constant, while the water is flowingthrough an orifice of a predetermined size, the process of the presentinvention provides the desired constant flow rate of the water supply.There are several means available which permit the maintenance of aconstant hydrostatic pressure directly at the orifice. Generally,applicable for this purpose are the commercially available pressurevalves, which by diaphragm and springs or other means provide an even,predetermined water pressure at the orifice regardless of reasonablepressure variations which might occur upstream in the water supply line.However, reliable, accurately operating instruments of this type arerather expensive and may require constant maintenance and service tokeep them in top operating condition.

In accordance with my invention a simple device may be used for thecontrol of the rate of flow of the water. In spite of its apparentsimplicity the novel device operates trouble-free for long periods oftime, requiring only a minimum of care and maintenance.

Various embodiments of this device are shown in FIGS. 19 to 21 of myPatent No. 3,124,051 and are described in said patent. Special referencethereto is made herewith.

Another preferred embodiment of the water metering device is illustratedin FIG. 1 of the accompanying drawings.

The metering device 3100 comprises principally three vertical tubes3101, 3102 and 3103, running side by side and being mounted on abackrest 3104. Tube 3102 in the center is advantageously made wider thantube 3101 and/ or 3103. Giving it a cross section 4 to 5 times that oftube 3101 was found desirable, :as it reduces turbulence in the flowpattern of the water in tube 3102. The top end of tube 3101 iscommunicatingly connected to the bottom section of closed funnel-likereceptacle 3106, opening 3107 in the top. Receptacle 3106 containsoverflow funnel 3109, the narrow bottom section of which iscommunicatively connected to the top end of tube 3102, which penetratesthrough the bottom section of receptacle 3106. Tube 3103, which alsopenetrates the bottom of receptacle 3106 in sealing relationship isextended upwardly and communicatively joined to a side Wall section ofoverflow funnel 3109. The horizontal edges 3110 at the top end ofoverflow funnel 3109 serve as overflow passages for the incoming water.The free bottom end 3118 of tube 3103 is bent to a vertical directionand provided with means for communicating connection of tube 3101 to asource of running water such as tap water (not shown).

To the bottom end of the centrally positioned tube 3102 is removablyjoined orifice 3112, which together with the bottom end of tube 3102 issurrounded and contained by aerated but otherwise closed funnel-likereceptacle 3114, with outlet 3115 at the bottom. The lower end 3117 oftube 3101 is bent to the left and provided with means forcommunicatively connecting tube 3101 to conduit, leading to a sink orother water disposal means. The device is advantageously hung by eye3116 to a wall or other support, preferably in a generally verticalorienta tion. This mode of support assures at all times essentiallyvertical orientation of the device, increasing the accuracy andreproducibility at all times. The metering device may however also beattached by the bottom end of the backrest directly to a photographicbath or to any other desired supporting means.

The operation of the device corresponds in many ways to that of themetering devices described hereinbefore. Tube 3103 is connected to asource of running water, which flows upwardly in said tube 3103,entering overflow funnel 3109 and flowing downwardly in tube 3102,leaving it through orifice 3112 and outlet 3115, from where it may beled to a heating chamber or to a photographic 'bath by suitable conduit,as described hereinbefore. By providing the water, entering through tube3103 at a flow rate exceeding the rate of flow of water through orifice3112, tube 3102 will soon be filled with water, the excess of which,when it has reached horizontal edges 3110 of overflow funnel 3109,overflows continuously into receptacle 3106, from where the excess waterleaves through tube 3101 to flow into a sink or other place of disposal.

The stream of water, emanating from outlet 3115 is accurately metered asdescribed hereinbefore. The accuracy of the device may be readilyadjusted to the needs and re- 6 quirements in the particular use forwhich the device is designed. Increasing the total length of tube 3102and/ or increasing the size of the horizontal top opening of receptacle3106 will tend to increase the accuracy of the metering device. It was,however, found that a degree of accuracy, required for the purposes ofmost photographic processes could be readily achieved with devices,having relatively short tubes 3102. Lengths of tube 3102 of one or twofeet have excellent results in most instances, sometimes shorter lengthswere found satisfactory. Only rarely will it be necessary to give tube3102 a length greater than two feet. As is readily ap parent, the justdescribed embodiment of the metering device may be readily made fromplastic materials e.g. by extrusion methods and/or injection moldingmethods or by the use of pre-extr-uded plastic tubing and parts,requiring simple assemblage and low labor cost, thus permittingeconomical eflicient mass production of the device.

If desired, the water metering device of the invention may be furthermodified by running the water in two or more stages, i.e. by usingmetered water as the feed water, including again an excess in a secondmetering device. This expedient permits sometimes to achieve evengreater accuracy. It is important to note, that for highest accuracy ofthe metering device of the present invention the stream of water,emanating from the orifice, should be permitted to fall freely for atleast one inch or so. Placing an obstruction close to or at the orificewill usually affect the accuracy and often reduce the amount of waterflowing from the device per unit of time.

As has been shown, the device and process of the invention are operatedby the provision of a column of water of substantially constant heightover a fixed orifice, through which water flows at a substantiallyconstant rate, which rate is determined by the size of the orifice andby the hydrostatic pressure exerted by the water column of controlledheight. It is of advantage to use an orifice which has a relativelylarge opening e.g. of one or several millimeters up to one centimeter ormore and preferably of 2 to 6 mm., depending on the dimension and sizeof the apparatus. The expedient of using relatively wide orifices willavoid plugging or partial obstruction of the orifice by particlescontained in the water supply and carried to the orifice with thestreaming water. If a narrow orifice is desired to be used, a filter orsieve of a pore or mesh size, which will hold back particles ofappreciable size, may be placed upstream of the orifice e.g. into theinlet tube of the metering device. Thus, the effective size of theorifice may be readily kept constant by avoiding its partial obstructionby foreign matter. Occasional cleaning of the orifice will assist inmaintaining the desired effective size accurately. If desired, thesocalled self-cleaning type of orifice may be used.

The proper ratio of orifice size to the height of the column or to thehydrostatic pressure, respectively, depends on the amount of water whichis desired to be delivered per time unit and on the particular design ofapparatus used. Experiments have shown that one liter of water perminute passes through an orifice of approximately 3 to 4 mm. diameter,if it is under the hydrostatic pressure exerted by a Water column ofapproximately 20 cm. height. Proper orifice size and height of the watercolumn can be readily established by simple tests or by calculation forany desired rate of water flow. The above values will serve as anindication of the relationship of the factors. Doubling the crosssectional areas ofthe orifice, while maintaining the height of the watercolumn constant will approximately double the rate of water flow throughthe orifice. Depending on the size of the photographic treatingapparatus, several hundred cubic centimeters to several liters of waterper minute will be suflicient to accomplish the aims of the presentinvention.

As was shown hereinbefore, the height of the water column is readilymaintained at a constant value or level by feeding the water, upstreamof the orifice, at a rate exceeding the desired downstream flow andremoving the excess water by way of an overflow. Highest accuracy isachieved if the linear extension of the overflow is kept as large aspossible under the circumstances. In the practical operation theoperator need only observe the overflow and adjust it in such way thatit does not cease at the lowest line pressure expected during anyoperating session. Adjustment and readjustment of the rate of overflowis possible without any adverse effect on the accuracy of the method.

If desired the hydrostatic pressure exerted by the water column may besupplied by a diaphragm-spring arrangement which is adjusted to providethe desired water pressure at the orifice. It may be of a type whichpermits escape of excessive amounts of water through an overflow ventingtube. Other pressure controlling devices may be used with similarly goodeffect.

By the steps and device described in the foregoing a stream of water ofconstant rate of flow and of known constant temperature (temperaturereading A) emerges from the downstream side of the orifice. In order toraise the temperature of this stream of water to the desired value, e.g.75 F. it is only necessary to supply the differential in heat energy tothe water. The approximate heat energy required per minute may becalculated by multiplying the specific heat of water with the amount ofwater emerging from the downstream side of the orifice and the numberdegrees of the temperature differential between the desired workingtemperature and the measured temperature of the incoming water supply.The heat energy can readily be calculated as its electrical energyequivalent which may be supplied to electrical heating elements andconverted to heat energy which in turn is transferred upon the waterstream. Usually the electrical energy supplied to the heating element orelements may need to be slightly higher than the values calculated bythe equivalency of electrical and heat energy. A constant factorrepresenting the efliciency of the particular heating element and theheat losses inherent in the particular device can readily be determined.The data and corrective factor thus established may form the basis forthe determination and calculation of the electrical energy required tobring about the desired temperature change in a given apparatus underreproducible conditions, and can be incorporated in an emperical factoror equation which can be used for all successive operations.

For practical operation of the process it is only necessary to multiplythe electrical energy, required for the raising of the temperature ofthe incoming water by one degree, with the number of degrees representedby the difference of the desired temperature B minus actual measuredtemperature (temperature A) of the incoming water. Multiplying theelectrical energy thus calculated by said empirical factor will directlygive the electrical energy requirement for a given apparatus to producea stream of water of constant temperature regardless of the initialtemperature of the incoming water, the only requirement being that thetemperature of the incoming water and its flow rate be constant over theduration of the operation. 7

A convenient means of adjusting the electrical energy, fed to theheating elements, to the temperature of the incoming water-this beingthe only variable in a system in accordance with this embodiment of thepresent inventionis a continuously variable resistor which may beincluded in the electrical heating circuit. The resistor may be providedwith markings which indicate the correct setting required for eachtemperature of the incoming water (temperature A). Thus a single settingof the resistor or rheostat to the temperature marking indicating theactual reading of the temperature of the incoming water willautomatically provide for the correct temperature of the water leavingthe device at the outlet side.

The preferred modification of the apparatus of the in.- vention does notrequire a high powered resistor or rheostat. The temperature controldevice in this preferred embodiment of the apparatus comprises primarilya multiplicity of heating elements which are suitably varied with regardto their full heating capacity and consumption of electrical energy. Byproper combination and correlation of two or more of the multipleheating elements any desired increase of the temperature of the knownamount of water of known constant temperature, passing by the heatingelements per time unit, can readily be achieved by switching in or outone or more of the heating elements as needed without the undesirablegeneration of excessive heat and loss of electrical energy in therheostat or resistor. Closest control of the temperature of the waterstream by simple and inexpensive device and construction is thuspossible.

The temperature of the incoming tap water may vary from theapproximately 32 to 75 F. or higher depending on the season of the yearand the special local conditions. A minimum of six heating elements ofvarious definite capacities are needed to cover the range from 32 to 75F. in steps of 1 F. Covering this range in steps of 2 P. will requirefive heating elements of correspondingly spaced capacities. With stepsof 5 F. the number of heating elements may be reduced to only three.Economy of construction and simplicity of design make it desirable toemploy the smallest possible number of heating elements, if this can beaccomplished without sacrificing the desired close control of thetemperature of the outgoing stream of water say within i /z F. Thisaccuracy is possible to a very high degree by the provision of threemajor heating elements with the said 5 F. steps of capacity and of anadditional smaller heating element whose capacity covers the gap of 5 F.left by the major heating elements. This additional or adjuvant heatingelement may be rheostatically or thermostatically controlled as will beshown hereinafter, providing the fine control of the temperature withina 5 F. range.

A temperature control arrangement which may be used with advantage inthe practice of the present invention, employing four heating elementshas been illustrated in FIGS. 2226 of my Patent No. 3,124,051 to whichspecial reference is made herewith.

Instead of controlling the major heating elements by the actuation ofindividual switches, as shown in FIG. 3 of the attached drawings asoptional feature, one may with advantage employ a switching arrangementas is shown in FIGURES 23 and 24 of my Patent No. 3,124,- 05 1.

It is generally preferred that the range of temperature increase orcapacity provided by the adjuvant heating element and its coordinatedrheostat to be somewhat larger than the temperature gap actually to becovered. The device is thus made more flexible by the fact that it iscapable of providing temperature increases larger than that required bythe gap left by the major heating element combination. Depending on thecircumstances and conditions the adjuvant heating element and thecoordinated rheostat, if such is used, may be designed to cover up todouble or three times the gap i.e. 4 to 6 degrees or more in the case ofa 2 degree gap and up to 10 degrees 01' more in the case of the 5 degreegap. With this provision the device is capable of meeting even the mostunusual conditions such as line voltage deviations of 20% or more aswell as other unusual conditions in the rate of water supply, extremeheat losses by low room temperature and so forth.

If desired, a thermometer may be provided in the water stream,downstream of the main heating elements but upstream of the adjuvantheating element. The additional thermometer permits the taking ofintermediary readings of the preheated water which can be directlyutilized for the setting of the rheostat. This mehod provides for evenhigher accuracy and convenience in the operation of the process, becauseit compensates for any inaccuracies and deviations introduced by aninaccurate rate of flow of the Water stream and by uncontrollablefluctuations of the voltage of the power supply. As can be readilyvisualized, deviations of the flow rate of the water stream or of theelectric power of for instance percent will in the case of the twodegree step result in a deviation of the final temperature of theoutgoing water stream of only 0.2 F. and with the five degree step ofonly 0.5 R, if the expedient of taking intermediary readings on theadditional thermometer is used. These deviations are the maximum andwill often be smaller depending on how much of the capacity of theadjuvant heating element is utilized. Deviations of O.2 to 0.5 F. fromthe desired mean value are acceptable even in those photographicprocesses which require the most exacting temperature control. Using thedirect method of heating the water stream by a single correspondinglyhigh powered rheostatically controlled heating element a deviation ofthe line voltage of 10 percent from its mean value would result in adeviation of the temperature of the outgoing water by at least 3 F. inthe case of a temperature reading A of 45 of the incoming water. Themethod of the invention can be made to be even more accurate, if this isdesired, by providing a second independently rheostatically controlledadjuvant heating element. The capacity of this element need be onlysmall to serve for the compensations found necessary by the reading ofthe downstream thermometer, which in this case would be placeddownstream of the first adjuvant heating element.

Of course, variations of the line voltage may also be compensated byadjustment of the electrical power input into the heating elements as agroup e.g. by the provision of a master rheostat in the power supplyline which is adjusted in accordance with readings taken from a voltmeter at the power line. If desired, any of the commercially availablevoltage stabilizers may be used with equal benefit. However, any of thehigh powered equipment of this type is rather expensive and will not bein reach of the average amateur photographer. The rheostats employed inthe device of the present invention, as described hereinbefore, aredesigned for a small power input and thus relatively inexpensive.

In a further modification of this device the rheostats and thermometersare dispensible if the adjuvant heating element in thermostaticallycontrolled. This modification is the preferred one because of itscompletely automatic operation and independence of any reasonablefluctuations of flow rate and line voltage. The small power input of theadjuvant heating element permits the use of a relative small thermostatwhich should be accurate within /2 or better A" F. and optionally F. Thethermostat will be employed with the above described switch device ofwhich only the rheostat and its controls have been omitted. Theperiodical opening and closing of the power supply by the thermostatwill only aifect and act on the adjuvant heating element thus producingonly small fluctuations of the water temperature between on and offcycles. This is much to be preferred to the relatively largefluctuations of the water temperature between on and off cycles whichcannot be avoided if a high powered heating element is controlled by acorrespondingly larger thermostat.

The thermostat and its heat sensitive element are generally locateddownstream of all heating elements including the adjuvant heatingelement controlled by it. As has been mentioned, the thermostat opensand closes the power supply to the adjuvant heating element only anddoes not affect the supply of electricity to the major heating elements.An even higher accuracy and completely automatic temperature control,independent of fluctuations in the water supply and of the line voltage,can be achieved by combining the above described switch device, withthree major and one adjuvant heating elements, with an additional verysmall powered auxiliary heating element which is independentlycontrolled by a small, sensitive thermostat.

As in the rheostatic control method described above, the adjuvantheating element is here with advantage also designed for a somewhathigher capacity than is needed to bridge the gap left by the majorheating elements. It is also of advantage to locate the thermostat in aposition in the water stream where it has a wide cross section andaccordingly a low flow velocity.

The heating element or elements, in any of the water temperature controldevices described hereinbefore are provided in a confined area throughwhich the stream of water passes. Though the orientation and arrangementof the heating elements relative to the path of the water stream is notcritical, it is generally preferred that the Water passes first over thehigher powered elements with the lowest powered or the adjustable andvariable element last. The heating elements are preferably designed insuch manner that they olfer a large surface to the flowing water forready heat exchange. Guide walls or bafiles, diverting the flow of thewater, for instance in a zig-zag manner permit a more compact design ofthe heating device. Obstructions or other means such as sudden turns inthe direction of the path of the water stream will assist in the mixingof the water so that it assumes the desired average temperature over itsentire cross section. In order to avoid accumulation of gas bubbles orgas pockets in the heating chamber or channel with the resultant loss inefiiciency of heat exchange between the heating elements and the waterit is generally of advantage to have the water stream flow at an angleto the horizontal and preferably slightly upwards. This expedientpermits any gas or air bubbles which enter the heating device or whichform therein by the effect of the heat at the heating elements(dissolved air and gases), to travel upwards by their own buoyancy inthe direction of the traveling water stream. Thus any undesirableaccumulation of air or gas bubbles in the heating zone is virtuallyimpossible.

An embodiment of the heating chamber, utilizing these expedients, isshown in FIGURES 25 and 26 of my Patent No. 3,124,051.

In another modification of the invention the water stream may flow in avertical direction, for instance in an alternating downward and upwardspath which may be oriented horizontally or vertically. The heating zonemay be designed as an integral part of the water metering device or ofthe photographic treating apparatus or water bath respectively or, ifdesired, as an independent selfsufficient unit. The latter may find wideuse in applications other than for photographic treating apparatus. Inits application to the photographic processes and apparatus employing abath for temperature control the heating chamber is located between thewater metering device and the water bath surrounding the vessels ortroughs. In order to assure an even, uniform flow rate of the waterstream through the system certain critical limitations must be observedwith respect to the relative vertical positioning of the various units.The orifice of the metering unit should be located higher than thehighest point reached by the Water in the heating chamber or unit. Thelatter may be located higher or lower than the level or surface of thewater in the bath surrounding the vessels or troughs. However, theorifice of the metering device must in any event be located higher thanthe surface of the water in the bath. At least an inch and preferablyseveral inches up to 10 inches or more height differential will ensuresteady, trouble-free flow of the water stream from the metering devicethrough the heating device into and through the water bath and fromthere into the sink or other place of disposal. The individual devicesor units, if not constructed as a unitary device or apparatus, may beconnected by tubing or pipes or other suitable conduit.

In a preferred embodiment of the invention the heating chamber islocated in a low position such as underneath the bottom of the waterbath, where it may form an integral part of the latter as is shown, forinstance, in FIGS. 30 and 31 of my Patent No. 3,124,051 to which specialreference is made herewith.

Another embodiment of the composite bath and heating chamber of thepresent invention, described and illustrated in my Patent No. 3,236,649and in my copending application Ser. No. 342,029, filed Feb. 3, 1964, isequally useful, offering all the advantages of the invention asdescribed hereinbefore.

As stated hereinbefore, the rheostats described herein as the means forcontrolling the heat output of the adjuvant heating element may beconveniently substituted by voltage regulators such as variable voltagetransformers which are provided with suitable scales and markingsindicating the temperature values or differentials in the settings ofthe regulator.

The heating chamber or the heating devices of the present invention maybe provided with a multiplicity of heating elements of essentially equalheating capacity instead of the elements having different stepped downheating capacities. In either embodiment of the heating device of theinvention, when it is operated with a stream of water of a predeterminedconstant rate of flow, each heating element can be assigned atemperature value or a temperature rating, which equals and simplyexpresses the number degrees, by which the temperature of the stream offlowing water is raised by the particular heating element, when it isoperated with full capacity. If the heating elements in a givenapparatus are selected such that they have, for practical purposes, thesame or at least essentially the same heating capacity, the operator canachieve a desired rise of the temperature by switching or plugging in anumber of heating elements corresponding to the quotient of thetemperature diflerential (desired temperature minus actual temperatureof the incoming water) rounded to the next lower integer. The adjuvantvariable or thermostatically controlled adjuvant heating element isalways used. The heating capacity of the adjuvant heating element shouldwith this arrangement be at least equal to and preferably essentiallyhigher than the capacity of the main heating elements, so as to becapable of supplying the heat energy required to bring the watertemperature to the exact level between the said temperature values orratings of the uncontrolled heating elements.

By way of example, if the temperature value or rating of the mainheating elements is 6 F. and the temperature of the water is to beraised from 42 F. to 68 F., four main or full capacity heating elementsmust be switched in and additional heat energy, corresponding to atemperature value or rating of 2 F., is to be supplied by the adjuvantheating element. The output of the adjuvant heating element may bereduced to this value either by reducing the input of electric energycorrespondingly or by reducing the on-time accordingly, e.g. by the useof a thermostat which shuts for the adjuvant heating element or elementsintermittently off such that it supplies in a given time period just therequired heat energy. The just described embodiment of the heatingdevice may be conveniently constructed for the use of commerciallyavailable immersion heaters which are provided in the flowing stream ofwater. Each heater may be supplied with its own on-off switch or withprovisions for plugging it in or out of operation. To avoid accidents,it is naturally desirable, to ground all electrically conducting partsin the heating devices of the present invention in accordance withaccepted standards. It is also beneficial to incorporate into theheating device at least one device which protects the apparatus foroverheating e.g. in the case that the operator accidentally energizesthe heaters prior to the opening of the water supply. The said safetydevice, such as a thermostatically controlled on-ofl switch controllingthe main power input is conveniently placed close to or between theheating elements, so that any rise of temperature beyond thatencountered in the normal operation of the device will immediately shutoff all power to all heating elements. The shut-off control may be setat a relatively low temperature such as F. The temperature of e.g. 120or P. will never be reached in the heating device in normal operationunless the water flow is completely or at least partially blocked orunless the heating chamber is run dry.

An embodiment of the heating device of the present invention,incorporating the just described principles, is illustrated in FIGS. 2and 3 of the accompanying drawings. Cylindrical heating device 3150comprises cylindrical receptacle 3151, made up of cylindrical wall 3152and bottom 3153 and lid section 3154. Water inlet tube 3158 enters thecylindrical wall 3152 at a position close to the upper edge, to continuedownwardly as an integral conduit 3159 alongside the inside of thevertical cylindrical wall 3152 to a location close to the bottom 3153 ofreceptacle 3151, communicatively connecting into the circular flat cell3161 located underneath perforated distributor plate 3162. Horizontalplate 3162 is joined to the lower portion of cylindrical wall 3152 andprovides even distribution of the flowing incoming water over the wholehorizontal cross section of the receptacle 3151 by perforations 3164through which the water passes. A troughlike circular overflow 3166 isprovided horizontally around the inside of the upper portion ofcylindrical wall 3152. Trough 3166 is communicatively connected tovertical conduit 3169, which extend vertically downwards along theinside of the cylindrical wall 3152, penetrating the said cylindricalwall at a position close to the bottom and continuing as outlet tubing3170. The upper edge of circular trough 3166 is located at a level as isrequired for keeping the water at the desired level in the receptacle3151 which is needed to insure the complete immersion in the flowingwater of the hot parts of the heaters 3172 at all times.

The receptacle 3151 is covered by lid 3174 with drainage hole 3175 intowhich the immersion heaters 3172 and thermostatically controlled safetyshut-off switch 3176 are removably fastened so as to extend verticallydownwardly, with their electrical connections above the lid 3174 andwith their heating elements and hot parts extending into the waterpassing through the receptacle 3151. To the lid is joined dome-shapedcover 3179 with opening 3180 at its apex, through which the electricalconductors 3177 serving the heater and safety shut-off switch are led tobe connected to a multiple switch arrangement and to the source ofelectricity (not shown).

If desired, individual switches 3173 may be provided for the individualheaters for the energization and deenergization of the heatersindependently of each other.

The cover 3179 is perforated around its base and at its top so as topermit circulating of air, preventing overheating of the space above thelid. The lower peripheral perforations 3182 serve also the purpose ofdraining any liquid or water which should accidentally find its wayinside the cover, thus reducing the danger of shock and the accidenthazard appreciably.

The heating device may be operated as described hereinbefore. A streamof water of a measured temperature and of a predetermined constant flowrate enters through inlet tube 3158, flowing downwardly therein intocell 3161 and is evenly distributed by perforated distributor plate 3162to flow upwardly in the receptacle 3151, passing by the energizedheating elements 3172. Thereafter the water, with its temperature raisedto the desired higher level leaves the heating chamber by overflowinginto circular trough 3166 and from there to vertical conduit 3169leaving the receptacle 3151 through outlet tube 3170. From there it maybe conducted into a composite apparatus comprising a photographic bathand inserted therein treating vessels, where it is to serve as thetemperature conditioning and/ or washing medium.

The heating chamber may conveniently be produced from plastics by theinjection blowing or vacuum forming methods or by other suitablemethods, preferably with the inlet and outlet conduits and, if possible,the distributor plate all integrated in the design of the receptaclemaking the production a one step operation. Alternatively, thedistributor plate may be inserted and joined to the chamber subsequentlyby attaching it in essentially liquid tight relationship to a suitablerim 3186 provided in the bottom portion of the chamber.

The lid 3174 is advantageously made from metal e.g. by stamping and theheating elements are inserted therein removably in the usual manner e.g.by the use of threaded nuts etc. The construction of the lid from metalpermits the grounding of all metal parts by one grounding wire, thussimplifying the construction of the device and at the same timeincreasing the safety. The dome-shaped cover 3179' is advantageouslymade from plastic and is removably joined to the lid, so as to permitaccess to the electrical connections and wiring and the exchange of theheating elements, if this should be necessary. With the just describedconstruction, the operator does not run the risk of electric shock,because all electrically conducting parts are enclosed by electricalinsulators. The overheating protection device 3176 prevents fire hazardand removes the danger that the parts of the device soften or melt dueto overheating of the device.

The heating device may be provided with a smallpowered thermostat, whichis provided close to the water outlet 3170. A thermostat 3190 has beenindicated in dotted lines in FIGS. 2 and 3. The thermostat may be wiredto control one of the heating elements 3172 or preferably an additionaladjuvant heating element (not shown) of small heating capacity, having atemperature value of e.g. 2 or 3 F. and being provided within theheating chamber next to the elements 3172. Though the heating device ofthe present invention is operative and produces excellent resultswithout the use of a thermostat,

the provision of the thermostat renders the operation stillmore accurateand provides fully automatic operation, as has been explainedhereinbefore.

As is well known, the use of voltage stabilizers or regulators isrecommended to be used in the exposure of color negatives in theenlarger so as to insure consistent results and consistent predictablecolor rendering. By the provision of suitable electrical connections andswitches one and the same variable transformer or other voltageregulator may be used for the voltage control of both the adjuvantheating element in the temperature control device of the presentinvention as exemplified, for instance, in FIGS. 2 and 3 of the attacheddrawings, and of the light in the enlarger. The brief periods of timerequired for the actual exposure are too short to bring about anyappreciable falsification of the temperature in the treating baths, whenthe adjuvant heating element is briefly disconnected because it doesusually contribute relatively little heat energy to the water. Moreadvantageously, one may employ in accordance with the invention amodified variable transformer in which the movable brush and the controlmeans on the output side are duplicated so as to be operable andadjustable independently of each other. Accordingly, each of the outputbrushes and its controls can be used independently of the other, suchthat one brush may serve and control the adjuvant heating element andthe other brush controls the enlarger lamp. As can be readily seen, thecircuit of the adjuvant heating element need not be broken with thisembodiment of the -modified variable transformer when an exposure is tobe made. The enlarger circuit is not materially affected by the powerdrawn from the heater circuit as long as the transformer is designedwith a capacity enabling it to carry the combined load. The enlargercircuit is provided with a voltmeter, permitting the adjustment of thevoltage in the enlarger circuit to a predetermined, constant level everytime an exposure is made, independently of the power output required forthe adjuvant heating element.

Conveniently, the circuit of the adjuvant heater e.g. one of the heaters3172 in FIG. 2 of the attached drawings is supplied by the brushnormally provided on the transformer. The slidable brush or othercontact means serving the second or the enlarger circuit may be arrangedin various ways as is convenient and desired for the particular needs ofoperation. In those embodiments of the variable transformer, in whichthe brush or other slidable contact means are arranged opposite thecircular face of the transformer windings, the adjuvant brush mayconveniently be placed at and in sliding contact with the windings ofwire located at the opposite unoccupied circular face of thetransformer. Suitable changes and variations in the design of thetransformer make this arrangement practical and useful for the purposesof the present invention.

With the commercially available transformers it was found, however, tobe preferable to locate the adjuvant brush or slideable contact meansopposite the peripheral portion of the transformer windings. Since thevoltage in the enlarger lamp is to be controlled in a relatively narrowrange to be maintained at a predetermined value close to the inputvalue, it is generally not necessary that the adjuvant brush serving theenlarger circuit is capable of rotating fully around the periphery ofthe transformer. Complete control of the enlarger lamp is possible ifsaid adjuvant brush is adapted to cover only a small segment of theperiphery of the cylindrical transformer windings.

An embodiment of a variable transformer modified in accordance withthese principles is illustrated in FIG. 4 of the accompanying drawings.Cylindrical core 3400 carries all around windings 3401 of insulated wirewound on a winding form surrounding core 3400. The exposed sides of thewires at the circular face 3402 of the body are stripped from insulationso as to permit the passage of electricity between said wires and brush3403, which is slideably and rotatably contained on rotatable lever 3404mounted on rotatable shaft 3407. The core 3400 and shaft 3407 aremounted on and contained in base 3409.

Outside the cylindrical periphery of core 3400 is fixedly mounted toperpendicular extension 3411 of base 3409 cross sectionally triangularmember 3414 comprising partial cylindrical face 3415 and circular slot3416 both being located concentrically with the axis of core 3400.Adjuvant brush 3417 is set, with the use of suitable taps 3420 andmechanical means in insulating fashion with member 3414, so that it isslideable in a partial circular path and in contact with the windings ofthe transformer. The portions of the windings contacted by adjuvantbrush 3417, as it travels in its partial circular path are stripped attheir surface from insulation so as to establish electrical contactbetween the individual windings and the adjuvant brush 3417 in itsvarious settings.

The adjustment of adjuvant brush 3417 to the various positions providingthe desired voltage may be achieved by the provision of insulated knob3421 at an extension of t-a'b 3420 and its mechanical holding means. Thevariation of the position of adjuvant brush 3417 may also be achieved bythe use of gears and other suitable mechanical means which cooperate toforward brush 3417 to the desired setting by rotating a shaft providedat the front of the transformer.

The enlarger circuit connected to and supplied by adjuvant brush 3417includes advantageously a voltmeter indicating the voltage in saidcircuit. Provision of marks, preferably of luminescent marks at thepointer and at the position on the scale corresponding to the desiredvoltage facilitate the adjustment of the line voltage to the desiredvalue prior to the making of an exposure in the enlarger and make itpossible to make suitable adjustment by moving adjuvant brush 3417 tothe appropriate position on the windings of the transformer, even in thedark. As can be readily seen, the operation of the enlarger circuit doesnot affect the operation of the heater circuit, and both circuits can beindependently adjusted to the voltage required in the respectivecircuits, even though both are fed by a common variable transformer, asmodified in accordance with the present invention, which may find manyuses for purposes other than in the temperature control device of thepresent invention. The rheostats and/ or voltage regulators or variablevoltage transformers, respectively, are conveniently combined with theswitches and other electrical means required for the operation of theheating device and/ or of the enlarger, so as to form one centralcontrol panel for the electrical controls needed in the operation of theapparatus and process.

In the embodiments of the invention specifically described hereinbefore,the exact temperature in the stream of flowing temperature conditioningmedium is achieved by assuring a constant flow rate of the stream ofwater and adjusting the heat input so that exactly the quantity of heatis supplied which is required to achieve the desired temperature. Thepresent invention comprises also .an embodiment of the process andapparatus, in which the quantity of heat supplied, is kept constant,while the rate of flow of the stream of water or the throughput per timeunit is adjusted and controlled, so as to produce exactly the desiredtemperature in the stream of water.

This concept is employed with greatest advantage in :an embodiment ofthe process and apparatus which combines this concept with the principleof using a multiplicity of heaters as described hereinbefore. Theapparatus comprises as before means for metering a stream of water,heating means, and means for the control of the heating means. With theheat energy input kept constant, one varies the flow rate of the streamof water, so as to .adjust the quantity of water to be heated to theheat energy available per unit of time, to achieve an essentiallyconstant temperature of the stream of water. This expedient can bereadily achieved by employing in the apparatus variable metering means,which are preferably an orifice having a variable aperture and means,which .are capable of automatically controlling the aperture size oravailable opening of the orifice in relation to changes in the voltageof the power supply.

This may be achieved, for instance, by the placing of a movableconstricting means into the aperture of the orifice, which constrictingmeans is capable of either completely or partially closing the apertureor moving completely out of the way, so as to permit unrestricted flowof the water through the aperture. The constricting means arefurthermore adapted to assume any intermediary position, so as to permitthe passage of the water at any desired rate. The motion and relativepositioning of the constricting means is directly controlled by thewattage in the supply line to the electrical heater, e.g. by the use ofmovable electromagnets or magnets in a spool of wire, through which theelectric power flows before it enters the heating elements.Advantageously, the means are connected by suitable mechanical means tothe said restricting means, such that the rate of flow of water isdirectly proportional to the electrical or heat energy available at thevarious line voltages. In this manner, continuous control of the rate offlow of the stream of water can readily be achieved as a function of theline voltage, providing automatically a constant ratio of the quantityof water to be heated per time unit and the heat energy provided by theheating elements, thus assuring a constant temperature of the stream ofwater at all times, without requiring any attention of the operator tothe fluctuations in the line voltage and without requiring the use of acostly, high powered voltage stabilizer. As is readily apparent, theadjustable voltage controlled orifice is only needed in locations whereuncontrolled heavy fluctuations in the line voltage can not be avoided.

If a source of incoming water is available, which has l ab o ly Constanttemperature, that is a temperature, which does not fluctuate by morethan /2 F. the stream of water, emanating from the apparatus employingthe just described principle or in an apparatus of the invention whichis operated at reasonably constant line voltage, will be constant at alltimes within :L-% F. and thus satisfy the most exacting requirements inany of the photographic processes available today.

If in a particular location the source of incoming water does not havean absolutely constant temperature, it may be of advantage to provide inthe metered stream of water, upstream of the heating elements, athermostatically controlled auxiliary heating element of relativelysmall heating capacity, e.g. one having a rating of 2 F. i.e. one, whichhas a capacity high enough to heat the stream of water by 2 P. if it iscontinuously on, which assures that the incoming stream of water isheated to a slightly higher, but constant temperature, which then servesas the basis for the setting of the heater controls as described herein.This expedient may be conveniently combined with the voltage controlledadjustable orifice, if the instability of the line voltage makes thisdesirable.

The foregoing discussion shows that the process and apparatus of thepresent invention may be readily adapted to meet even the mostunfavorable conditions in the water and power supply without detractingfrom the accuracy and reliability of the process and apparatus of theinvention. Thus, even under diflicult circumstances a continuous streamof temperature conditioned water is readily provided for the carryingout of the photographic processes. As shown, the process and apparatusof the invention provide also the possibility of making the control ofthe temperature automatic, requiring only a few initial temperaturereadings and settings and yet providing an extremely high accuracy inthe temperature control over long operating sessions, which cannot bereadily achieved with similarly inexpensive equipment by the methods andmeans known in the prior art. The operator who wishes to economize inthe initial investment and who is willing to make occasionally duringthe operation of the process and apparatus of the invention a fewtemperature readings and if necessary, a few adjustments in the settingof the rheostate, or variable transformer or other control means canachieve perfect temperature control at every little expense and with theminimum of attention and effort. This flexibility of the equipmentrenders the process and apparatus of the invention useful for most anysituations, as they may occur in the practice of photographic processesby the inexperienced amateur, by the skilled and demanding amateur or bythe professional.

The water metering device and the heating chamber and, if desired, thevarious auxiliary components described hereinbefore may conveniently becombined to a unitary apparatus with suitable conduit provided in thedevice, to make the required communicating connections for theestablishment of the flow pattern in accordance with the foregoingteachings. The apparatus may be completely enclosed and need be providedonly with a water inlet connection, an outlet connection for the excessof running overflow water, an outlet for the stream of meteredtemperature conditioned water and electrical connections, powering andcontrolling the heating elements in the heating chamber and, ifnecessary, the electrical adjuvant devices.

The features, components and elements described hereinbefore withrespect to specific embodiments of the various devices and componentsmay be modified in many ways and/or recombined to form new embodimentsof the apparatus and devices of the invention.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it isunderstood, that the invention is not limited to the specificembodiments thereof, except as defined in the appended claims.

I claim:

1. A device which is adapted for controlling and maintaining thetemperature in photographic developing equipment at a desiredtemperature B, which device comprises means capable of providing acontinuously flowing stream of water, having an essentially constantflow rate and an essentially constant temperature A, which temperature Ais lower than the said temperature B, said device comprising in additionat least one heating chamber and means which are adapted to pass throughthe heating chamber said continuously flowing stream of Water, anddisposed in said heating chamber a multiplicity of electric immersionheaters, each of said heaters having a known heating capacitycorresponding to a temperature value, the sum total of the temperaturevalues of said heaters being at least as high as the maximum temperaturedifferential between temperature A and B for which the device is built,each of said heaters being provided with on-off switching means, wherebyonly those heaters and as many of the heaters are activated, whosetemperature values add up approximately to the temperature differentialby which the flowing stream of water is to be heated to achieve the saidtemperature B.

2. The heating device of claim 1, in which the heaters have differentheating capacities and temperature values.

3. The heating device of claim 1, which comprises in addition at leastone ajuvant heater in combination with means which are adapted tocontinuously vary the heating capacity and the temperature value of saidadjuvant heater or heaters.

4. The heating device of claim 1, which comprises in addition anadjuvant heater in combination with a thermostat, which thermostat isprovided in the stream of water, downstream of the heaters, and whichthermostat is adapted to control the operation of said adjuvant heaterby suitable switching means.

5. The device of claim 1, in which at least one of the heaters isconductively connected to control means adapted to control the electricpower fed to said heating element from zero to the full rated input.

6. The device of claim 5, in which said control means is a continuouslyvariable transformer controlling the electric power input of at leastone heating element.

7. The device of claim 1, in which a thermostat is positioned downstreamof 011 heating elements, in contact with the flowing water stream andcontrolling the electric power input of at least one adjuvant heatingelement. 1

8. The device of claim 6, in which said variable transformer is adaptedto control independently of the heater circuit the voltage of a secondelectrical circuit containing the lamp of a photographic enlarger.

9. The device of claim 1, in which said means for the provision of acontinuously flowing stream of water of essentially constant flow rateis a device which comprises a vertically oriented, oblong receptaclehaving a water inlet, a water outlet comprised of an orifice ofpredetermined aperture size in a low position in said receptacle andoverflow means at a position essentially higher than said water outlet.

References Cited UNITED STATES PATENTS 1,183,925 5/1916 Waters 219-4861,746,522 2/ 1930 Carleton 219-307 1,772,834 8/ 1930 Hopkins -961,792,757 2/1931 Parker et a1. 137-577 X 1,967,889 7/1934 Kitroser 95-941,985,280 12/1934 Carleton 219-296 X 2,690,764 10/1954 Hotfmann 137-5632,743,909 5/1956 Lawlor 137-563 X 2,790,890 4/1957 Kasuga 219-2872,852,232 9/1958 Marwell -30 2,969,451 1/1961 Logan 219-306 X RICHARD M.WOOD, Primary Examiner. C. L. ALBRITTON, Assistant Examiner.

